This invention relates to a controlled deflection roll such as is used in the papermaking industry for establishing nipping contact with a mating roll. More particularly, this invention relates to a method and apparatus for virtually eliminating contact between the hydraulic oil used to actuate the roll shell support elements, commonly called shoes in the industry, and the atmosphere. Still more particularly, this invention relates to the separation of the hydraulic oil used to actuate the roll shell support element from the oil used to lubricate the roll bearings.
In prior, and current, controlled deflection rolls, the hydraulic fluid, which is a petroleum based oil, is introduced to the interface between the roll shell support shoes and the cylindrical inner surface of the roll shell either hydrostatically, through capillary tubes extendingfrom beneath the pistons providing the supporting force beneath the shoes through the shoe to the interface, or is supplied to the inner surface of the roll shell to provide hydrodynamic force when the oil being carried along the inner surface of the roll shell is wedged between the leading edge of the shoe and the roll shell to establish a hydrodynamic film, and roll shell supporting pressure, between the shoe and the roll shell.
The deleterious effect of exposing petroleum based lubricants to the atmosphere, particularly at elevated temperatures, is well-known. Also known is the desirability of heating and cooling the hydraulic oil used to provide the deflection compensating force within a controlled deflection roll, such as used in the papermaking industry, and the oil used to lubricate the bearings in such rolls. Examples of such prior art is shown and described in U.S. Pat. Nos. 4,282,638; 4,282,639 and 4,679,287. The selective heating and cooling of the bearing lubrication and roll shell support oil requires these lubricants to be circulated between the interior of the roll and exterior heating, cooling and pumping equipment. In order to provide this recirculation of these oils, they must be collected within the interior of the roll shell and conducted out of the shell through suitable conduits. Since the interior of a controlled deflection roll is relatively large in diameter, there is a relatively large interface between the atmospheric air within the roll and the pool of bearing oil and/or support element (shoes) actuating oil. Accordingly, over a relatively short period of time, depending on oil temperature and the size of the interface between the atmosphere and the oil, the lubricants become oxidized, begin to lose their lubricating properties, and deposit solid deleterious material on system components.